89009-10-9Relevant academic research and scientific papers
A 'one pot' synthesis of polysubstituted pyridines from metallated alkylphosphonates, nitriles and α,β-unsaturated ketones
Palacios, Francisco,Ochoa De Retana, Ana M. Ochoa,Oyarzabal, Julen
, p. 4577 - 4580 (2007/10/03)
A simple and efficient synthesis of polysubstituted pyridines is described. The key step is based on the regioselective addition of lithiated β-enaminophosphonates 5 to unsaturated carbonyl compounds 3. Pyridines 1 can also be obtained in 'one pot' reaction from phosphonates 6 when these compounds are metallated followed by addition of nitriles and unsaturated carbonyl compounds.
Pyrylium Compounds. XVIII. 2-Alkoxy-2H-pyrans from Tetra- and Pentasubstituted Pyrylium Salts
Fischer, Gerhard W.,Zimmermann, Thomas,Weissenfels, Manfred
, p. 729 - 741 (2007/10/02)
Alkali alkoxides add regioselectively to 2,3,4,6-tetrasubstituted pyrylium salts 7 (R'=H), affording high yields of colourless crystalline 2-alkoxy-2H-pyrans 9.The latter are also formed simply on refluxing 7 in the corresponding alcohol with triethylamine as proton acceptor. 3,5-Dialkylsubstitued 2,4,6-trialkylpyrylium salts react analogously.The 2H-pyran structure of the adducts obtained follows from their n.m.r., i.r., u.v. and mass spectra as well as from their reaction with tetracyanoethylene to cycloadducts of type 10.Acids regenerate from 9 the original pyrylium cations, whereas reaction of 9 with nitromethane or ethyl cyanoacetate provides benzene derivatives. - The novel starting pyrylium salts 7b-o are characterized by u.v./vis data and by transformation into the corresponding pyridine derivatives.
